2-Chloro-3,3,3-trifluoropropene (HCFO-1233xf) represented by the chemical formula: CF3CCl═CH2 is a useful compound as an intermediate for producing various fluorocarbons, and also as a monomer component for various kinds of polymers.
A known process for producing 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) comprises reacting anhydrous hydrogen fluoride (HF) in a gas phase in the presence of a catalyst. For example, Patent Literature 1 listed below discloses a process comprising fluorination of 1,1,2,3-tetrachloropropene (HCO-1230xa) in a gas phase in the presence of a chromium-based catalyst. Patent Literature 2 listed below also reports a process in which HCO-1230xa is fluorinated in a gas phase, using a chromium-based catalyst.
However, the processes disclosed in the above literature are problematic in that since catalytic activity tends to deteriorate as a reaction proceeds, if the reaction is continued for a long period of time, catalytic activity decreases, resulting in decline in the selectivity of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf).
For example, Patent Literature 3 listed below discloses a process for preparing 2,3,3,3-tetrafluoropropene (HFO-1234yf) by using 1,1,2,3-tetrachloropropene (HCO-1230xa), 1,1,1,2,3-pentachloropropane (HCC-240db), or the like as a starting material, fluorinating the starting material with HF to produce 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), and then adding HF to the thus-obtained HCFO-1233xf to produce 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb), followed by a dehydrochlorination reaction. In this process, decline in catalytic activity as the reaction proceeds is also unavoidable in a first step, which comprises fluorinating HCO-1230xa, HCC-240db, or the like with HF in the presence of a fluorination catalyst such as a fluorinated chromium oxide to produce HCFO-1233xf. For example, Example 1 of Patent Literature 3, which describes a step of preparing HCFO-1233xf by reacting HCO-1230xa as a starting material with HF in the presence of fluorinated Cr2O3, discloses that the selectivity of HCFO-1233xf was decreased to about 83% after 650 hours of reaction time, and that the reaction was stopped due to loss of catalytic activity.
Patent Literature 4 listed below discloses a process comprising fluorination of 1,1,2,3-tetrachloropropene (HCO-1230xa), 1,1,1,2,3-pentachloropropane (HCC-240db), 2,3,3,3-tetrachloropropene (HCO-1230xf), or the like in the presence of a fluorination catalyst, in which catalyst deterioration is suppressed by adding an amine-based stabilizer, hydroquinone-based stabilizer, or other stabilizers.
However, according to this process, selectivity is decreased, and a satisfactory effect of suppressing decrease in catalytic activity cannot be attained. Thus, a periodic catalyst activation treatment is inevitable.
Patent Literature 5 listed below discloses a process in which 1,1,2,3-tetrachloropropene (HCO-1230xa) is reacted with HF in a liquid phase in the presence of an antimony halide catalyst. However, in addition to the difficulty in handling the catalyst, this process is not economical due to the occurrence of reactor corrosion, the necessity of waste treatment, and the like. Thus, the process is not suitable as an industrial production process. Furthermore, Patent Literature 6 listed below reports that 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) can be produced by reacting HCO-1230xa with HF in a liquid phase under catalyst-free conditions. However, because it requires a long reaction time due to a slow reaction rate; a large excess of HF; severe reaction conditions under high pressure; etc., this process is not suitable as an industrial scale production process.
As described above, a process for continuously producing 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) at a high yield in a simple and economical manner has not yet been established.